In a Long Term Evolution (LTE) system and an Advanced Long Term Evolution (LTE-Advanced) system, downlink physical layer control signaling contains Downlink Grant (DL Grant) information needed to be acquired by a terminal (for example, a User Equipment (UE)) and related to downlink transmission, and Uplink Grant (UL Grant) information needed to be acquired by the terminal and related to uplink transmission, to indicate various information related to transmission such as a location of a transmission resource, a way for modulating a code and etc, and these pieces of physical layer control signaling are transmitted on a Physical Downlink Control channel (PDCCH). The physical layer control signaling is mainly referred to as customer specific control signaling of a physical layer.
In Release (R) 8/9 of the LTE system and R10 of the LTE-Advanced system, a physical layer control channel over which a physical layer control signaling is transmitted is generally configured in the first N Orthogonal Frequency Division Multiplexing (OFDM) symbols, and generally the N symbols are called a control signaling transmission area.
The available transmission resources in an existing control signaling transmission area (a first control signaling transmission area, a first control signaling area) is divided into multiple Control Channel Elements (CCE) which are taken as Resource Elements (REs), a resource occupied by the control signaling is allocated by taking a CCE as a unit, i.e. as an RE. The CCE may be further subdivided into a Resource Element Group (REG), one CCE is composed of multiple discontinuous REGs. Generally one CCE includes 9 REGs and each REG is composed of multiple basic REs.
Both specific and common control signaling are transmitted by taking a CCE as an RE, and then are mapped to corresponding REG resources, and then are mapped to Resource Elements (the minimum resource unit) of multiple Physical Resource Block (PRB) pairs (which are also called PRBs for short).
Blind detection is generally performed by a terminal in the following ways: computing initial locations of specific control signaling and common control signaling, wherein the specific control signaling is mainly concerned usually. An Aggregation Level (AL) of blind detection and blind detection times are shown in Table 1.
TABLE 1Blind detection space Sk(L)Size of blind detectionType of controlspaceTimes of blindsignalingALL[in CCEs]detection M(L)UE-specific166 (6/1) 2126 (12/2)482 (8/4) 8162 (16/8)Common4164 (16/4)8162 (16/8)
It can be seen from Table 1 that, a control signaling transmission resource allocated for a user is not continuous, which brings many difficulties to implementation of a closed loop precoding technique in an multi-antenna system, resulting in that only a diversity technique can be used and the closed loop precoding technique can hardly be used in the control signaling area.
In a release after R10, in order to improve a transmission capacity of a control channel and to make the control signaling to be capable of supporting more users, a new control channel area (a second control signaling transmission area, a second control signaling area) is developed, and the control signaling transmission resource of the same terminal may be a continuous time frequency resource, to support the closed loop precoding technique and improve a transmission performance of the control signaling.
The control signaling areas of new and old releases are shown in FIG. 1, a part of transmission resources may be allocated from a Physical Downlink Shared Channel (PDSCH) transmission area of an original R8/9/10 to act as a new control signaling transmission area, so that transmission of the control signaling supports the closed loop precoding technique, a capacity of the control signaling is increased, and control signalings of more users can be supported. A control channel transmitted in the second control signaling area may be called a second control channel or an enhanced PDCCH (ePDCCH).
A method for ePDCCH detection is introduced respectively in the following aspects such as, resource granularity detection, a location for ePDCCH transmission (an ePDCCH candidate), a pilot frequency port, a transmission way, and etc.
In general, a base station may first notify a terminal of an ePDCCH resource set. The base station and the terminal may also predefine a basic resource allocation element, and then predefine a size of several occupied resources (which is generally aggregation of one or more resource allocation elements), and the aggregation of N resource allocation elements is called AL N. Generally a basic resource element, namely an enhanced Control Channel Element (eCCE) is defined, and a function of the eCCE is the same as that of the CCE. In a second control area, the eCCE may borrow a definition of the CCE or slightly modify the definition, or may also make a new definition. The size of the eCCE may be constant or variable. The eCCE may contain a Distributed eCCE (D-eCCE) and a Localized eCCE (L-eCCE) as shown in FIG. 2 and FIG. 3.
The control signaling may define different ALs based on the eCCE, for example a Localized-type AL set is {1, 2, 4, 8} or {1, 2, 4, 8, 16}, and then different ALs denote different sizes of resources. A Distributed-type AL set is {1, 2, 4, 8, 16} or {1, 2, 4, 8, 16, 32}, and thus the terminal can perform blind detection directionally on corresponding ALs.
Currently, a total set of ALs available for detection may be determined according to some specific cases, as shown in Table 2 or Table 3.
TABLE 2NECCENormal subframes and special subframes,configuration 3, 4, 8, with nEPDCCH <104 and using normal cyclic perfixAll other casesLocalizedDistributedLocalizedDistributedtransmissiontransmissiontransmissiontransmission221144228844—16—8
TABLE 3NECCENormal subframes and special subframes,configuration 3, 4, 8, with nEPDCCH <104 and using normal cyclic perfixAll other casesLocalizedDistributedLocalizedDistributedtransmissiontransmissiontransmissiontransmission221144228844161688—32—16
A base station may configure multiple ePDCCH resource sets for the terminal, each ePDCCH resource set may uniquely corresponds to a type such as a Localizetype D (which is called a type L for short) or a Distributetype D (which is called a type D for short). The type of the ePDCCH resource set and an ePDCCH transmission type are the same, the type of the ePDCCH resource set and the ePDCCH transmission type may be Localized or Distributed. The type is referred to that if the type of the ePDCCH resource set is set as a distributetype D, then only Distributed ePDCCHs are transmitted or detected in the ePDCCH resource set; if the type of the ePDCCH resource set is set as a localizetype D, then only Localized ePDCCHs are transmitted or detected in the ePDCCH resource set.
In general, when a Distributed ePDCCH is detected in the Distributed-type ePDCCH resource set, detection may be performed in accordance with the aggregation of L-eCCEs. When a Localized ePDCCH is detected in the Localized-type ePDCCH resource set, the detection may be generally performed in accordance with the aggregation of Localized eCCEs.
Since a terminal is limited due to complexity, there is always a certain limitation to a total number of times of blind detection, and there is just a little difference between the number of times of blind detection in a case of less ePDCCH resource sets configured and that in a case of more ePDCCH resource sets configured. Therefore, a technical problem to be solved is how to determine the number of times of blind detection or the amount of the ePDCCHs allocated by each ePDCCH resource set to further determine ePDCCHs needed to be detected in each ePDCCH resource set.